Bent and tempered glass is used extensively for vehicle side and rear windows to provide good resistance to breakage as well as an aesthetically appealing shape that complements the design of the vehicle. In order to perform the bending and tempering, sheet glass must be heated to its deformation point of about 1200.degree. to 1300.degree. F. and then bent to the required shape before being rapidly cooled by an air spray in order to temper the glass. Tempering greatly increases the mechanical strength of the glass and its resistance to breakage as well as causing the glass to break into small relatively dull pieces when broken instead of into large sharp slivers as is the case with untempered glass.
One manner in which glass is bent and tempered is with press benders having shaped surfaces between which heated glass in clamped to shape it prior to being air cooled by a quench unit to provide tempering. U.S. Pat. Nos. 3,454,389; 3,476,542; 3,488,178; 3,600,150; and 3,951,634 disclose press bending and tempering apparatus for sheet glass.
Sheet glass is also bent and tempered by heating of planar glass sheets while supported on bending molds including movable sections. Prior to softening of the glass during heating, the sections of the mold are oriented to accommodate for the glass sheet planarity. Upon softening of the glass sheet as it is heated, the mold sections move relative to each other under the force of gravity acting on the sheet and the mold sections in order to provide bending of the sheet prior to rapid cooling thereof which provides its tempering. Thin glass, i.e. on the order of 1/8", cannot be bent by this apparatus since it does not have sufficient weight to actuate the pivoting of the mold sections until the glass becomes so soft that it overbends. U.S. Pat. Nos. 3,269,822; 3,278,287; 3,307,930; and 3,365,285 disclose this type of bending and tempering apparatus.
Heating of glass sheets prior to bending and tempering thereof has also been performed on fluid support beds as the glass is conveyed through a furnace. Normally the support bed is inclined slightly with respect to the horizontal so that gravity engages an edge of the glass with a movable frame that provides the impetus for glass movement along the bed. There is no contact between the bed and the oppositely facing surfaces of the glass during the conveyance as the glass is heated. This lack of contact prevents marring and scratching of the soft surfaces of the glass as the glass reaches its deformation temperature. However, there normally is mechanical contact with the glass during the bending after the heating in preparation for a cooling quench that tempers the glass in its bent condition. U.S. Pat. Nos. 3,497,340; 3,607,187; and 3,607,200 disclose glass bending and tempering apparatus of this type with a fluid support bed.
Vacuum forming of heated glass sheets is disclosed by U.S. Pat. No. 3,778,244 wherein the sheet glass is first heated during conveyance along a roller hearth conveyor. After heating, a lifter with a curved downwardly facing surface has a vacuum applied thereto about the surface to shape the glass. After shaping against the curved surface of the lifter, the vacuum is terminated to drop the glass onto a mold for conveyance to a waiting operator who removes the glass from the mold. Further vacuum forming of the glass to a curved surface of the mold is also disclosed.
Other bending and tempering apparatus for sheet glass is disclosed by U.S. Pat. Nos. 2,223,124; 2,348,887; 2,646,647; and 2,085,520.